DLPS052 October 2015 DLPA3000
The illumination function includes all blocks needed to generate light for the DLP system. In order to set accurately the current through the LEDs a control loop is used (Figure 5). The intended LED current is set via IDAC[9:0]. The Illumination driver controls the LED anode voltage VLED and as a result a current will flow through one of the LEDs. The LED current is measured via the voltage across sense resistor RLIM. Based on the difference between the actual and intended current, the loop controls the output of the buck converter (VLED) higher or lower. Which LED conducts the current is controlled by switches P, Q, and R. The Openloop feedback circuitry ensures that the control loop can be closed for cases when there is no path via the LED, for instance when ILED= 0.
Within the illumination block, the following blocks can be distinguished: